This invention relates in general to catalytic cleaning devices for motor vehicle exhausts and in particular to a new and useful catalytic cleaning device for attachment to a motor vehicle exhaust pipe which has a transition portion of a housing with an inner shell therein.
Similar known devices include an inner shell which extends along the outer circumference of a monolith and a spacer matting is arranged between the housing and the inner shell. The not very precise positioning of the inner shell by the spacer matting is considered to be a disadvantage.
Furthermore, it is known that the inner shell may extend along the inside of the housing in the region containing the monolith, and the spacer matting can be arranged between the inner shell and the monolith, whereby the inner shell is joined to the housing in the connection regions, and not in the monolith containing region. Again, the inner shell is positioned with insufficient accuracy in the monolith containing region.
Finally, it is known that the inner shell can be placed in the transitional regions and welded to the housing in each particular connection region. At the transitional region, each end of the inner shell engages with a ring, being able to move relative to the lengthwise direction, while the other axial end region of the ring is secured to the housing. In this way, the sliding fit between the part of the inner shell and the ring is located in a zone with intense admission of exhaust gas. Furthermore, the retention of the monolith solely by the spacer matting between the housing and the monolith is not sufficiently stable in its positioning.